The analysis tools and databases that are part of the standard analysis environment defined by the SSC-LAT working group are tabulated below. (Development efforts for any tools or databases not in the standard environment are not within the scope of the working group.) For each tool and database, summaries of the requirements are being prepared. Entries in the tables below have links to any existing draft requirements summaries, and a single file with all of the drafts combined is available in Word or PDF format (7 May 2002, now out of date).
The databases in the analysis environment are quite varied in the content and access methods. The most central, that for the Event summary information for gamma rays and the corresponding pointing/livetime history, will likely be managed in a true database system. Access to these will be via special utilities that construct queries and format the results. The analysis tools will read these formatted results rather than communicate with the databases directly. This division is made in the interests of portability and maintainability of the software. The other databases may not actually be managed in a database system, owing to their relatively small sizes or the likely access methods. Still, within the analysis environment they are still classified as databases because they provide (static) input to the analysis tools.
The utilities include the data extraction tools described above plus tools for calculating exposures and for defining gamma-ray source models, all of which are essential in supporting the analysis tools. Another utility envisioned is a general plotting and image display tool, which also supports the analysis tools.
The core of the analysis tools in the standard environment is the likelihood analysis tool for source detection and characterization. Other analysis tools are defined for specific aspects of pulsar or GRB analyses. Another analysis tool supports quantitative evaluation of counterparts for point sources. The interstellar emission model, which is central to the likelihood analysis, is provisionally defined as an analysis tool rather than as a database because it will have adjustable parameters.
Two tools are defined for high-level simulation of observations, one to generate a simulated pointing/livetime history, and the other to generate the corresponding simulated high-level event summary data for gamma rays. These will be essential for validating the analysis tools and perhaps eventually also for proposal planning.
A growing collection of step-by-step procedures for performing common high-level analyses of LAT data is available here. The descriptions of the procedures include specific references to the tools and databases in the standard analysis environment.
For databases, the requirements summaries primarily contain statements about the contents of the databases and how they are accessed. This is the essential information for showing how the databases and analysis tools are integrated into an analysis environment. Other important requirements, such as for data ingest rates, have been under consideration by the SSC-LAT working group, and will be incorporated later in the full requirements documents.
|
ID |
Name |
Description |
Last Updated |
Doc. |
|
D1 |
Event summary (Level 1) |
Summary information (i.e., everything needed for post-Level 1 analyses) for photons and cosmic rays, possibly segregated by event classification |
25 April 2002 |
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D2 |
Pointing, livetime, and mode history |
Timeline of location, orientation, mode, and accumulated livetime |
7 May 2002 |
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D3 |
Point source catalog |
Summary information for LAT-detected point sources, from which the LAT point source catalog is extracted |
25 April 2002 |
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D4 |
Other high-level databases, e.g., GRB, transient summaries |
Useful subsets of the point source database |
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D5 |
Pulsar ephemerides |
Timing information (maintained during the mission) for a set of radio pulsars identified as potential LAT sources |
14 May 2002 |
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D6 |
Instrument response functions |
PSF, effective area, and energy redistribution functions in CALDB format |
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The user environment in general (e.g., scripting and a common GUI interface that ties together the analysis tools) may fall under this category as well.
|
U1 |
Event data extractor |
Basic front end to the event summary database (D1) |
25 April 2002 |
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U2 |
Pointing/livetime history extractor |
Basic front end to the pointing, livetime, and mode history database (D2) |
1 May 2002 |
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U3 |
Exposure calculator |
Uses IRFs and pointing, livetime, & mode history; plus special version for short time intervals |
24 May 2002 |
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U4 |
Map generator |
Binning of photons, regridding of exposure, coordinate reprojection, calculation of intensity |
23 April 2002 |
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U5 |
Catalog access |
Extracting sources from catalogs, LAT and otherwise |
24 April 2002 |
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U6 |
Event display |
This would probably be desirable, although not actually an analysis tool post Level 1. It would require access to the Level 0 & Level 0.5 data for a given event |
|
[Covered by instrument simulation software effort] |
|
U7 |
Source model definition tool |
Interactive construction of a model for the region of the sky by specifying components (interstellar emission, point sources, extended sources), and parameter values; optionally can produce an intensity map of the model |
7 May 2002 |
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U8 |
Image and plot display |
This is integrated with the other analysis tools |
22 Apr 2002 |
|
A1 |
Likelihood analysis |
Point source detection, characterization (position, flux, spectrum), generalized models for multiple/extended sources |
31 May 2002 |
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A2 |
Source identification |
Quantitative evaluation of the probability of association of LAT sources with counterparts in other catalogs |
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A3 |
Pulsar phase assignment |
Phase assignment to the output of U1 or A5; other tools (such as exposure generation U3, map generation U4, and likelihood analysis A1) shall recognize specification of phase interval |
6 June 2002 |
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A4 |
Pulsar profiles |
Applies energy and inclination dependent cuts to the output of U1 to select gamma rays near a specified direction; for pulsars the tool can construct phase-binned histograms and apply periodicity tests, or passed to A4 if the period is not known. |
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A5 |
Pulsar period search |
Search for periodic emission from a point source |
30 May 2002 |
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A6 |
GRB spectral-temporal analysis |
Non-parametric characterization of a burst |
23 June 2002 |
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A7 |
GRB physical modeling |
Fits a GRB physical model to LAT or LAT+GBM data for a GRB |
23 June 2002 |
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A8 |
Interstellar emission model |
Not software per se, although the model itself will likely have parameters (or more complicated adjustments) that need to be optimized once and for all, in concert with an all sky analysis for point sources. TBD whether interstellar emission of the LMC will need to be included in the model. |
26 April 2002 |
|
O1 |
Livetime/pointing simulator |
Generates simulated pointing, livetime, and mode histories (analogue of D2) for a specified time range and observing strategy. This should be available as a tool, but probably most generally useful will be precomputed simulated D2 databases, which can be used subsequently for any study with O2. |
24 April 2002 |
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O2 |
High-level observation simulator |
Generates gamma rays according to the instrument response functions (i.e., after detection, reconstruction, and background rejection), bypassing the instrument simulation step |
24 April 2002 |
Last updated: 09/17/2002 10:53 -0700